1In mixing bowl, cream butter and sugars. Add egg, beat well. Combine flour, baking powder, baking soda and salt; add to creamed mixture alternately with sour cream. Fold in rhubarb. Fill paper lined or greased muffin cups three fourths full.
Combine the pecans, brown sugar and cinnamon in a small bowl; cut in butter until crumbly, sprinkle over batter.
3Bake at 350 degrees for 22 to 25 minutes or until a toothpick comes out clean, cool for 5 min.before removing from pans to cooling racks.